By Sarah McBride, Alexei Oreskovic and Gerry Shih SAN FRANCISCO (Reuters) – For technology executives weighing market flotations for Silicon Valley startups, this week's gangbusters Twitter Inc initial public offering sent a powerful signal: full speed ahead. Now, many – including Box, Square and Airbnb – are likely to accelerate their IPO plans, according to venture capitalists. File-sharing company Box picked Morgan Stanley, Credit Suisse and JP Morgan to lead its IPO, Reuters reported Friday. Twitter's lack of profits proved to be no obstacle to the micro-blogging site raising as much as $2.1 billion in its IPO.